Printing units of web fed printing presses, particularly those for newspapers, include printing mechanisms. Each printing mechanism generally consists of a transfer cylinder, a form cylinder, and an inking mechanism as well as a dampening mechanism. Such printing units also can have counter pressure cylinders and one counter pressure cylinder can interact with one or more transfer cylinders of different printing mechanisms.
Printing units also exist that do not have counter pressure cylinders. In such printing units, the transfer cylinders of two printing mechanisms roll off onto each other. Accordingly, a web fed rotary printing unit with several printing mechanisms comprises several form cylinders, as well as several transfer cylinders, and possibly one or more counter pressure cylinders. When the term “cylinder” is used hereinafter, it may refer in the context of the present invention to a form cylinder or a transfer cylinder or a counter pressure cylinder. Also, the term cylinder may refer to cylindrical rollers of an inking mechanism or a dampening mechanism that is involved in the printing.
With typical prior art web fed rotary printing units, each printing mechanism is assigned its own adjustable drive motor to actuate the transfer cylinder and form cylinder, as well as inking and dampening mechanisms of the particular printing mechanism. If a counter pressure cylinder is present, the counter pressure cylinder is also assigned its own drive motor.
With prior art printing units, there is no mechanical drive connection between the printing cylinders actuated by a drive motor. Instead, in the prior art, each of these printing cylinders is controlled in terms of its angular position and/or speed of rotation by its own controller, independently of the other printing cylinders. For this, the angular position, for example, of a printing cylinder is detected by means of a feedback value pick up and its signals are compared with a set point signal, in order to generate a control signal for the particular drive motor that is dependent on the deviation from the set point signal. The particular drive motors are responsible for the synchronization of the printing cylinders of a web fed rotary printing unit. As a result, distortion moments acting within a printing unit may additionally load or relieve the drive motors. For this reason, with prior art arrangements, the drive motors must be designed with very high motor power or torque, which is a disadvantage, particularly from the standpoint of cost.